Sandicor, the county's MLS, has added a text field to its listings that allows members to enter contact information, including names, email addresses and brokerage websites. The information, along with the usual listing data, would be disseminated by syndication websites such as ListHub and Point2, which are sources of information for popular real estate sites.

The main idea is that the contact information in the extra field would be displayed prominently for home hunters to see, nixing any confusion over the listing agent and an agent who is advertising on Trulia or Zillow.

"I think it will be clear to consumers if they want to contact the listing agent, they can," Sandicor CEO Ray Ewing said. "If not, they can contact others who have ads around (the listings.) We give them the choice."

Real estate brokers, who can opt-out of filling out the new field, also will benefit because the extra information will help drive traffic back to their websites, Ewing added.

It is believed Sandicor is the first MLS to make such a system change, Ewing said. But he adds that at least one real estate brokerage in the U.S. has something similar in place. He's referring to Howard Hanna Real Estate Services, a Pittsburgh-based company with 4,200 brokers and agents. Company president Howard "Hoby" Hanna told the U-T San Diego the change went in place the last quarter of 2010 to address the "proliferation of syndicated websites."

Sandicor said it has alerted ListHub and Point2 of the shift. Whether the companies pull in the new data is up to them, Ewing said. It's also important to note that real estate brokerages decide if they send their data to listing syndicators.

Zillow's response?

"I don’t see any direct impact to Zillow, but we haven’t talked to Sandicor about what this means," said company spokeswoman Cynthia Nowak. "In general, more information about a listing is in the best interest of consumers so we welcome it."

Trulia could not immediately be reached for comment. I've also put media requests to Point2 and ListHub, which is owned by Realtor.com.

UPDATE 10:34 a.m. ON WEDNESDAY: Luke Glass, general manager of ListHub, confirmed Sandicor notified ListHub of the change on Jan. 17. Glass' comment in a written statement: "At ListHub, we respect the rights of all brokers as the owners of the listing content, as well as their responsibility to market property listings in the way they believe is best for their sellers." I asked ListHub if it plans to pull in the new data. A spokeswoman said "not at this time."

Here's Trulia's response in a written email to the U-T San Diego: "At Trulia, we always make it easy for consumers to contact the listing data source and the listing agent based on the information provided to Trulia. In early January, we released a data pledge to this effect.

What did Point2 say?: It plans to pull in the extra data that San Diego MLS members may put into listings, said spokesman Roger Noujeim. He added: "If stricter distribution of data is the preferred choice for some MLSs, with the intention that consumers go on to the broker or agent site for more information, Point2’s systems will cater to that need."

The new feature will be available to Sandicor's 17,000 members starting Wednesday and more changes are coming.

Soon, the company will decrease the number of photos that can go out to syndicators to four, down from the maximum of 25. Another upcoming change: Images sent out to outside parties will bear watermarked contact information of the listing agents.

There's no doubt the discussion is about data and the control of data.

Here's proof of that from the last sentence of a letter sent out to Sandicor's members on the new-field change.

"Sandicor recognizes this new field as a vital and valuable data source for a member's online marketing endeavors," the letter says.